Photoexposure mechanism and contact printer therefor

ABSTRACT

A photographic artwork generating mechanism comprises a contact printer for exposing relatively large area images on a photosensitive surface in combination with another photoexposure device for drawing lines and/or for flashing small symbols on the photosensitive surface to complete the artwork by adding lines and other features to the image or images exposed by the contact printer. The contact printer may be operated either in a step and repeat manner or in a photo composition manner. In the step and repeat mode of operation, with each operation of the contact printer either a complete artwork or a complete artwork skeleton is exposed on the photosensitive surface. In the photo compose mode of operation, the contact printer is operated a number of times to compose a complete artwork or artwork skeleton from a number of exposures. In either mode of operation, when the contact printer is used to produce an incomplete artwork or skeleton, the artwork may be completed by using the second photoexposure device to add lines, small symbols and other features to the skeleton.

Webster PHOTOEXPOSURE MECHANISM AND CONTACT PRINTER THEREFOR [75] lnventor: Ronald B. Webster, Melrose, Conn.

[73] Assignee: The Gerber Scientific Instrument Company, South Windsor, Conn.

{22] Filed: Dec. 18, 1972 [21] Appl. No.: 316,010

[52] US. Cl. 355/19; 355/40; 355/91; 355/95; 355/99; 354/4 [51] Int. Cl. ..G03b 27/00; G03B 27/02; G031) 27/32 [58] Field of Search 355/40, 19, 91, 97, 99, 355/78, 95; 354/4 [56] References Cited UNITED STATES PATENTS 2,974,579 3/1961 Echelson et a1. 355/95 3,241,472 3/1966 Robertson 355/95 3,330,182 7/1967 Gerber ct a1 354/4 3,424,527 1/1969 Bremson, Jr...... 355/19 3,455,634 7/1969 Guffon 355/91 3,548,713 12/1970 Webster 354/4 3,652,158 3/1972 Burgess 355/91 3,673,937 7/1972 Mader 354/4 3,751,250 8/1973 Moscony et a1. l. 355/87 Sept. 9, 1975 Primary Exuminer-Richard M. Sheer 57 1 ABSTRACT printer either a complete artwork or a complete artwork skeleton is exposed on the photosensitive surface. In the photo compose mode of operation, the contact printer is operated a number of times to compose a complete artwork or artwork skeleton from a number of exposures. In either mode of operation, when the contact printer is used to produce an incomplete artwork or skeleton, the artwork may be completed by using the second photoexposure device to add lines, small symbols and other features to the skeleton.

2 Claims, 31 Drawing Figures PATENTEDSEP 191s SHEET PATENTED SEP 1975 SPEET .......I .....l..... D .0.

FIG. 5

FIG. 6

I/J....... .....E ...J MW .H. ....W...

00000000 000 00000w n 0000fi mm 0m0 0000 00 0 00000000 0 00 01000 QH 0 00000000 000 000005 0 0000a m w 0 mn0 00hhu000 000000 0 0 000 00000 H 0000Hm00u0 00 000 0 u0 0000 m 0 00d 000 00a w 0 00000000 0 000 000005 0 00004 0 w 0 0M0 000w000 0 000000 0 w 000 000005 00an 0 m 0 un 00ww 000 H 00000000 000 000005 ....n.. 0 00000 0 000 000005 0 "0Afi0 000 M 0 00ww0000 0 0000000 000 00000E 0000n 0 0 0 0 0000w000 n 000000 0 0 000 000 0E 00 900M 000 F0000 0 0000000 000 000005 0000 000 0 00000 00 0000000 000 0000E PATENTED 35F 91975 SHEET VZZ/Z/ PATENTEDSEP 191s SHEET FIG. I5

m Mr I W MB T 0% NE W who a 0u0 m w 1 L; 7 p f! w W FIG. l6

PATENTED SEP 1975 SHEET FIG. 26

FIG. 27

,A -zos PATENTEU SEP 1975 SHEET FIG.

SEC

SHOT

LOGIC COMMANDS FROM CONTROLLER [$24 PHOTOEXPOSURE MECHANISM AND CONTACT PRINTER THEREFOR BACKGROUND OF THE INVENTION This invention relates to devices for exposing photosensitive surfaces to generate artworks thereon, and deals more particularly with such a device including both a contact printer for exposing a relatively large area of such photosensitive surface in one operation and another exposure device for drawing lines on the photosensitive surface and/or for exposing symbols of relatively small area.

The photoexposure mechanism of this invention is particularly useful in situations where it is desired to produce a relatively large number of identical or generally similar two-dimensional artworks. Such artworks may, for example, be masks of the type used in the manufacture of printed circuit boards and integrated circuit chips or in chemical milling and photo engraving processes. The mechanism of this invention includes a contact printer of improved construction which is movable over a photosensitive surface and operable with each operation of expose a relatively large area of the photosensitive surface. The exposure made with each operation of the contact printer may be such as to represent either a complete artwork or only a portion of an artwork which is subsequently completed by further exposure of the photosensitive surface. The contact printer includes a photo mask in the form of a plate which is held in direct contact with the photosensitive surface during a printing operation by a unique vacuum system which eliminates distortions of the photomask and photosensitive surface which otherwise might produce inaccuracies in the exposure.

In addition to being used by itself, the contact printer may also be used with a second photoexposure device, forming part of the mechanism of this invention, adapted to expose lines and other small symbols on the photosensitive surface. This permits the contact printer to be used to expose standard outlines, formats and repetitive patterns, and the other exposure device to be used to complete the artwork by adding lines and other small features to the image exposed by the contact printer. For example, in the manufacture of printed circuit boards, very often a number of different boards will use an identical basic format of contact fingers, bus lines and socket pads and will differ from one another only with regard to wiring lines drawn between these basic elements. Such wiring is sometimes referred to as discretionary wiring" as it is wiring which is added to the basic or standard circuit board format, at the discretion of the designer, to convert the standard format into a specific circuit board configuration. Therefore, when producing circuit board masks of different specific configurations but ofa standard format, the mechanism of this invention may have its contact printer equipped with a master photomask bearing the stan dard format so that with a single operation of the contact printer the entire basic format of the circuit board is exposed on the photosensitive surface. Then the second photoexposure device may be used to expose or draw-in the discretionary wiring. This avoids the need for drawing the entire circuit board configuration with the line drawing device or for providing the contact printer with a master photomask for each specific circuit board desired.

SUMMARY OF THE INVENTION This invention resides in a mechanism for exposing artworks on photosensitive surfaces, which mechanism consists of a means for supporting a sheet of photosensitive material, contact printing device, a second photoexposure device for exposing lines and small symbols, and a meansfor driving both the contact printing device and the second photoexposure device over the photosensitive surface to enable the contact printer to be brought into registry with selected areas of the photosensitive material and to enable the second photoexposure device to be moved along any desired line relative to the photosensitive material.

The invention also resides in the construction of the contact printer, especially the means included in such printer for holding the master photo mask thereof in direct contact with the photosensitive material during exposure. This construction includes a main frame, a base frame movable vertically relative to the main frame and having a relatively large opening parallel to the photosensitive material. The base frame opening is located adjacent the surface of the photosensitive material and receives a master photo mask in the form of a plate which is supported along its edges from the adjacent edges of the base frame by a gasket which pneumatically seals the plate to the base frame and resiliently supports the plate so as to allow it to move a small distance vertically relative to the base frame. The base frame includes a downwardly facing peripheral pneumatic seal gasket movable into and out of contact with the photosensitive material as the base frame is moved toward and away from such material, and a vacuum system is provided for introducing a vacuum into the space surrounded by the pneumatic seal gasket. The vacuum system and the means for moving the base frame are so controlled that in a printing operation the base frame is first 'moved downwardly to bring the pneumatic seal gasket into contact with the photosensitive surface, and then vacuum is applied to the space surrounded by the seal gasket to cause the base frame and the master plate to be urged by atmospheric pressure into direct contact with the photosensitive material. Another vacuum holddown system is used to hold the photosensitive material to its supporting surface The invention further resides in the utilization in the contact printer of an eIectro-luminescent panel as the light source for illuminating the associated photo mask, and in the photomask being divided into a number of separate discrete areas and the electro-luminescent panel being divided into a similar arrangement of discrete areas, each of which overlies a corresponding respective one of said discrete areas of said photo mask, which are selectively energizable to enable the selective illumination of different areas of the photo mask.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a perspective view showing a photoexposure mechanism embodying this invention.

FIG. 2 is an illustration showing schematically the basic parts of the mechanism of FIG. I.

FIG. 3 is a partial plan view of the aperture wheel of the line drawing and symbol flashing photoexposure device of the mechanism of FIG. 1.

FIG. 4 is a partial view of the master photo mask plate used in the contact printer of the mechanism of FIG. 1.

FIG. 5 is a view showing the image-exposed on the photosensitive surface by operation of the contact printer of the mechanism'of-FIG; I. FIG. 6 is similar to FIGQS but shows a completed artwork m'ade'by adding lines, through the use of the line drawing device of the mechanism of FIG. 1, to the FIG. 5 skeletonal image. v

FIG. 7 is a side elevational view of the contact printer and line drawing device of FIG. '1.

FIG. 8 is a front elevational view'of the Contact printing device of FIG. '1' with the light unit and'top cover in place.

'FIG. 9 is a perspective view of the contact printer of FIG. 1 with the top cover removed and with the light unit in place.

' FIG. 10' is a perspective view similar to FIG. 9 but shows 'the'light unit and master plate removed.

FIG. 11 is a perspective view showing the contact printer light unit by itself.

FIG. 12 is a perspective view showing the contact printer master plate by itself.

FIG. 13 is a vertical sectional view through 'the mastcrplate taken on the line 13-13 of FIG. 12.

FIG. 14 is an enlarged front elevational view of the contact printer of themechanism of FIG. 1 with the top cover, light unit and master plate removed and with certain parts being shown broken away to reveal the structure of other parts.

FIG. 15 is a plan view of the contact printer with the top cover, light unit and master plate removed.

FIG. 16 is an enlarged fragmentary view showing a portion'of the base frame of the contact printer.

FIG. 17 is another enlarged fragmentary sectional view taken generally on the lines 17-17 of FIG. 16.

FIG. 18 is a sectional view taken on the line 18-18 of FIG. 15.

FIG. '19 is a sectional view taken on the line 19-19 of FIG. 14.

FIG. 20 is a sectional view taken on the line 20-20 of FIG. 14.

FIG. 21 is a sectional view taken on the line 21-21 of FIG. 15.

FIG. 22 is an enlarged view partly in vertical section and part in side elevation of the contact printer light unit.

FIG. 23 is a bottom view of the light unit of FIG. 22.

FIG. 24 is a vertical sectional view taken on the line 24-24 of FIG. 9.'

FIGS. 25, 26 and 27 are illustrations, in the form of schematic vertical sectional views through the contact printer, showing'the positions of the parts thereof at various stages of a printing operation.

FIG. 28 is a simplified schematic diagram illustrating the basic logic system for controlling the operation of the contact printer.

FIG. 29 is abottom view ofa light unit used in an alternatc embodiment of this invention.

FIG. 30 is a plan view of a master plate designed for use with the light unit of FIG. 29.

FIG. 31 is a schematic diagram showing a modificamechanism embodying this invention. Referring to this figure, the mechanism there shown consists of a table 30 having a flat upwardly facing work surface 32 for supporting a sheet of photosensitive material 34. The photosensitive material may be of various different forms, but generally consists of a glass, plastic or paper sheet having a photosensitive film defining its upper surface. Supported for movement relative to the work surface 32 in the illustrated X coordinate direction is a main carriage 36 straddling the .work surface 32, and mounted on the main carriage is a work carriage 38 movable relative to the main carriage in the illustrated Y coordinate direction. Therefore, by combined movement of the main carriage 36 in the Xdirection and movement of. the work carriage in the Y direction the work carriage and the devices attached thereto may be moved to register with any .point on the photosensitive material or to trace any desired line relative thereto.

The table 30, main carriage 36 and work carriage 38 are or may be parts of a conventional X-Yplotter of the type commonly used with pen or printing mechanisms attached to the work carriage for drawing graphics onto a sheet of paper or other material supported by the work surface. In any event, thetable 30 preferably tion of the logic system of FIG. 28 to adapt it for use with a multi-segment light unit such as shown in FIG. 29.

FIG. 1 shows in general a complete photoexposure includes a vacuum holddown system for holding the sheet of photosensitive material 34 to the work surface. Such vacuum holddown systems are well known. In the illustrated case such asystem is provided and consists of a large number of small openings 40, 40 passing through the material defining the work surface and connectible to a vacuum source. The work surface 32 is divided into a number of different sections to which the vacuum source may be selectively connected so that when the vacuum holddown system is in use only those openings 40, 40 covered by the sheet of photosensitive material may be connected to the vacuum source to prevent the loss of vacuum through uncovered openings. The vacuum drawn through the openings covered by the photosensitive material, of course, causes the photosensitive material tobe pressed to the work surface by atmospheric pressure.

In accordance with this invention the mechanism of FIG. 1 further includes a contact printing photoexpo sure device 42, for exposing relatively large area images on the photosensitive material 34, and a second photoexposure device 44. The second device is operable to expose lines on the photosensitive material 34, to flash symbols of relatively small area onto the photosensitive material 34, or to both'draw lines and flash small symbols. The contact printer 42 is of a unique construction as illustrated and described hereinafter in more detail. The secondphotoexposur'e device 44 may take various different forms but is preferably, and is taken herein to be, a device such as disclosed in US. Pat. No. 3,330,182 entitled A Device for Exposing Discrete Portions of a Photosensitive Surface to a Variable Intensity Light Beam." The construction of the de vice 44 is discussed hereinafter only in a general man'- ner and reference may be had to said US. Pat. No. 3,330,182 for a further understanding of its details. Completing the mechanism of FIG. 1 is a numerical controller'46, having a magnetic tape reader 48 as the input thereto: which automatically controls, in response to-the'input information supplied by the tape reader48, the'inovement of thc'carriages 36 and 38 and the operationof the photoexposure devices 42 and FIG. 2 is a schematic view showing the basic parts of the contact printer 42 and of the second photoexposure device 44. Referring to this figure and considering first the contact printer 42, this device consists basically of aphotomask 50 and a light source 52 for uniformly illuminating the photomask 50. The photomask is arranged parallel to and adjacent the sheet of photosensitive material'34 and between the material 34 and the light source so that when the light source is energized an image of the photomask is exposed on the-photosensitive material. During such exposure or printing the photomask is held direct contact with the photosensiti've" material as explained hereinafter. Within the broader aspects of this'invention the photomask may take various different forms, but preferably and as shown hereinafter, it consists of a glass plate bearing an image formed'by a layer of opaque material on its lower siirface ,"th'e opaque layer being present at some areas of the bottom surface and absent from other areas of the bottom surface as needed to define the master image. Therefore, the'mas'ter plate is in the form of a photographictransparency'the image of which is defined by the opaque material.

The second photoexposure device 44 of FIG. 2 consists of a light source which may take various different forms but which is shown to consist of an incandescent lamp 54 and associated mirror 56. Light from the light source and mirror passes through a condensing lens 58 to uniformly illuminate one aperture 60 of an aperture wheel 62. A real image of the illuminated aperture 60 is projected onto the surface of the photosensitive material by a projecting lens system 64. A light spot is thereby created on the photosensitive material 34 and by moving the photoexposure device 44 relative to the photosensitive material, to accordingly move the projected light spot over'the photosensitive material, a line may be generated or exposed on the photosensitive material as described in the aforesaid patent. The aperture wheel 62 contains a number of apertures any selected one of which may be brought into operative position in the path of the light rays from the light source to the projecting lens, and when the device is used for drawing lines'the selected aperture is generally one defining a round image or some other image of relatively simple geometry to create a correspondingly shaped light spot. Also, the aperture wheel 62 may contain other apertures with images representing symbols to be exposed orfthe photosensitive material 34. When such a symbol is to'be exposed, the appropriate aperture is brought into operative position while the device 44 is held either completely or relatively stationary relative to the photosensitive material and the light source is energ'ized momentarily to briefly project a real image of the aperture onto the photosensitive surface. Alternatively, the light source may be continuously energized and a shutter'which normally blocks the light' path be opernular series around the outer marginal edge of the wheel and held to the wheel by a plurality of holders 68, 68. Each aperture plate 66 defines a single aperture. However, it should be understood that here the term aperture is used to refer to the light transmitting area of a particular aperture plate, and such aperture may actually consist of a number of separate light transmitting areas. For example. an aperture may be in the shape of a lower case letter i and consist of two transparent areas, one being the body of the letter and the other the dOL'A number of the apertures, indicated at 70, 70, are of circular shape whereas the remaining apertures 72, 72 are of more complex shapes referred to for convenience as symbols. The circular apertures 70, 70 are used when the device 44 is used in a line drawing manner. That is, when drawing lines one circular aperture 70 is brought into the operative position to cause a circular light spot to be projected onto the photosensitive surface. The various circular apertures are of different diameters so that by bringing different ones of such apertures into the operative positiondifferently sized spots may be projected onto the photosensitive surface to generate lines of different width. The symbol apertures 72, 72 may vary widely in shape as required for the particular application to which the device 44 is put. For example, when thedevice is used in connection with the generation of printed circuit board photomasks, the symbol apertures 72, 72 may be in the shape of various Contact fingers, pads or other shapes commonly found on printed circuit board masks. Also, some of the symbol apertures may be in the shape of alphabetical ornumerical' sym bols to allow the exposure of numbers or letters onto the photosensitive surface through the symbol flashing process. The aperture plates 66, 66 of the aperture wheel 62 may, for example, either be in the form of thin metal plates wherein the apertures are formed by openings cut in the plates or may be in the form of'photographic transparencies each consisting of a sheet of transparent material and a layer of opaque material, the aperture of each aperture plate being defined by the presence and absense of the opaque material over various portions of the transparent sheet.

FIG. 4 shows a portion of an exemplary master photomask used in the contact printer of this invention. The illustrated mask 50 is designed for use in connection with making printed circuit board photomasks and consists of opaque areas 74 and transparent areas 76. The design or shape of the transparent areas 76 is accordingly the image of the master photomask and is the image exposed on the photosensitive material when the contact printer is operated.

FIG. 5 shows a portionof an exemplary image exposed on a photosensitive surface through the use of the contact printer of this invention. In this particular case the image, which is indicated generally at 78, is an incomplete artwork and in particular is in the" form of a basic format used by a series of different printed circuit board photomasks. Such incomplete artwork is sometimes herein referred to as a skeletonal art work, and it is later completed by exposing additional lines or symbols on the photosensitive material through use of the second photo'exposure device 42 of FIG. 1.

FIG. 6 shows a completed artwork asexposed on a photosensitive surface through the use of both the contact printer 42 and the second photoexposure device 44 of FIG. 1. Such completed artwork consists of the skeletonal image 78 of FIG. to which various lines, such as indicated at 80, 80, have been added through the use of the second photoexposure device 44. As mentioned previously, where the completed artwork is inthe form of a photomask for manufacture of printed circuit boards the additional lines 80, 80 added to the skeletonal art-work or basic format 78 is usually referred to as discretionary wiring and is wiring which converts the basic format to a specific circuit board configuration. Therefore, by printing standard formats through the use of the contact printer 42 and by adding discretionary wiring with the line drawing photoexposure device 44 a large number of different circuit board configurations may be exposed without changing the master photomask of the contact printer and without drawing the entire circuit board configuration with the device 44. In addition to merely drawing lines, the second photoexposure device 44 may also be used in the symbol flashing manner to expose symbols onto the photosensitive material to complete the artwork 78 of FIG. 5. Such symbols may be of various sorts and shapes and may, for example, be alphabetical and numerical symbols, as indicated generally at 82 in FIG. 6, used as to provide an identifying legend for the particular artwork in question. Of course, it will be understood that the contact printer need not necessarily be used in combination with a line drawing or symbol flashing device, and may instead be used by itself to expose complete artworks. To cause the contact printer to expose complete artworks it is of accessory only to provide it with a master photomask containing the image of a complete artwork. In either event, it will be noted that the sheet of photosensitive material 34 has an area considerably larger than the area thereof exposed by each operation of the contact printer. Therefore, the contact printer may be, and preferably is, operated in a step and repeat manner to expose a large number of identical images on the photosensitive material.

Reference is now made to FIGS. 7 to 28 for a more detailed description of the contact printing device 42 of FIG. 1. Considering first FIGS. 7 and 8, the contact printer 42 is there shown to be mounted to the work carriage 38 in front of the line drawing photoexposure device 44. The basic components of the contact printer include a main frame 82, a base frame 84, and a light unit 86. Another basic component is the master photomask 50, not visible in FIGS. 7 and 8, which underlies the light unit 86. The main frame 82 is fixed relative to the work carriage 38 so as to be held at a fixed height above the work surface 32 and so as to be moved relative to the work surface and the sheet 34 of photosensitive material supported thereby by movement of the work carriage 38. The base frame is generally rectangular in shape and is arranged generally parallel to the work surface 32. FIGS. 7 and 8 show the base frame in a raised position and from this position it is movable downwardly toward the work surface 32, as explained light unit 86 and releasably. connected to the main frame 82 by areleasable connector 90. A cover 92, shown in FIG. 8, normally covers the upper portion of the main frame.

As shown best in FIGS. 9 and l0,.the base frame 84 is generally rectangular in shape and includes a generally rectangular opening 94 arranged parallel to the plane of the worksurface. The main frame is in the form of a bridge which straddles the opening 94 to provide a space for receiving the light unit 86. v

The construction of the base frame is best shown in detail in FIGS. 14 to 17. Referring to these figures, the base frame adjacent the opening 94 has a horizontal upwardly facing shoulder 96 extending along and defining all four edges of the opening 94. Located midway along the length of each of the two portions of the shoulder 96 extending along the side edges of the opening 94 is an upwardly extending guide pin 98, shown in FIGS. 10 and 19. The base framehas a generally planar downwardly facing bottom surface 100 and on this surface is an elongated gasket surrounding the opening 94 and adapted to engage the photosensitive material supported on the work surface to create a pneumatic seal between the base frame and the photosensitive material as the base frameis lowered toward the printing position. This gasket, as illustrated, consists of a strip 102 of flexible material having one edge cemented or otherwise attached to the bottom surface 100, as shown in FIG. 17, and a flexible tube 104 receivedin a groove in the base plate so as to resiliently hold the free edge of the strip 102 slightly spaced from the bottom surface 100.

At the rear righthand corner of the base frame 84, as viewed in FIG. 15, a vacuum tube 106 is connected to the base frame and communicates with the bottom surface 100 and grooves 108 in the bottom surface, see FIG. 16, for introducing a vacuum to the space surrounded by the seal strip 102 for the purpose of holding the base frame and the master photomask in the printing position as explained in more detail hereinafter.

The vacuum tube 106 is connected by a flexible conduit 110 to a manifold tube 112. Also connected to the manifold tube is a supply tube 114, a vacuum gauge 116 and a vacuum switch 118. The supply tube 114 is connected to a suitable source of vacuum through a two-way solenoid operated valve, as hereinafter de-' scribed, for controllably admitting or exhausting vacuum from the manifold tube 112. The gauge 116 indicates the pressure existing in the manifold tube 1 l2 and the switch 118 operates an associated set of contacts when the vacuum in the manifold tube 112 reaches a predetermined value.

Respectively associated with each of the two sides of the main frame 82 are two downwardly extending legs 120, I20.to which the base frame is attached. FIG. 14 shows both of the legs 120, 120 in elevation and FIG. 18 is a vertical section through one of the legs, the other legibeing identical to that shown in FIG. 18. As shown in FIG 18, each leg includes two vertically spacedbearings 122, 122 which slidably receive a cylindrical post 12 4. The post 124, at its bottom end. is fixed to the basefrarne84 by being press fitted to a mounting pad 126 welded to the base frame 84. Upward movement ofth'e base frame 84 relative to the main frame 82 is limited by engagement of the lower ends of thelegs 120,120 "with t'heir associated mountv ing pads 126, 126. Thebziseframe is biased upwardly toward this raised position by a helical spring 128 in each leg 120 surrounding the post 124, the spring 128 being compressed between the lower bearing 122 and a collar 130 fixed to the post 124. To move the base frame 84 downwardly from the raised position shown in FIG. 18 each leg 120 of the main frame has associated therewith a solenoid 132 including a plunger 134 having a downwardly facing end engaging the upper end of the associated post 124. When the solenoid 132 is operated the plunger 134 is moved downwardly from the FIG. 18 position to accordingly push downwardly the post 124 and move downwardly the base frame 84.

In addition to the base frame being movable vertically relative to the main frame by operation of the solenoids 132, 132, it may also be rotated a small amount relative to the main frame about a vertical axis for the purpose of bringing the associated master photomask into accurate orientation relative to the X and Y axes of the work surface. That is, each master photomask consists of an image carried by atransparent plate and which image is fixed on the plate with respect to a set of reference X and Y axes also fixed relative to the plate. For proper operation of the contact printer the X and Y reference axes of the photomask plate should be exactly parallel with the X and Y axes of the work surface. Due to various small errors introduced during the making of a master photomask, when the master photomask is initially placed in the contact printer its reference axes may not precisely parallel the X and Y axes of the work surface. When the image of the master photomask is not properly angularly oriented relative to the axes of the work surface, it is said to be out of skew, and it is desirable to be able to adjust the base frame relative to the main frame to correct for this outof-skew situation.

Referring to FIGS. 14 and 15, the illustrated lefthand leg 120 is rigidly connected to the remainder of the main frame 82. The right-hand leg 120, however, is free to move a limited distance fore and aft relative to the remainder of the base frame. That is, as viewed in FIGS. 14 and 15, the main frame 82 at each of its ends includes a vertical plate 136. The left-hand leg 120 is permanently fixed to its plate 136. The righthand leg 120, however, is slidable fore and aft relative to its plate 136. Normally, the latter leg 120 is locked to its plate 136 by a knob 138. The knob 138 has a stem 140 fixed thereto which passes loosely through a horizontally elongated slot 142 in the plate 136 into threaded engagement with the body of the leg 120. When the knob 138 is tightened, the leg is clamped against the wall 136 and when the knob 138 is loosened the leg 120 is free to slide relative to the plate 136.

When the knob is loosened and the right-hand leg 120 is moved forwardly or rearwardly relative to the remainder of the main frame, the base frame 84 is rotated relative to the main frame about a vertical axis coinciding with the central axis of the post 124 of the left-hand leg 120. That is, the left-hand post 124 rotates in its leg 120 and serves as a pivot member.

Means for adjustably positioning the right'hand leg 120 in the fore and aft direction to rotate the base frame relative to the main frame is shown best in FIGS. 19 and and consists of a micrometer unit 144 having a barrel 146 fixed to the leg 120 and a spindle 148 extending through the leg 120 and engaging a stop 150 fixed to the remainder of the main frame. A tension spring 152 resiliently holds the free end of the spindle 148 in engagement with the stop 150. Therefore, it will be appreciated that when the knob is loosened operation of the micrometer unit 144 to advance or retract its spindle 148 will cause the right-hand leg 120 to be shifted rearwardly or forwardly relative to the re mainder of the main frame and to thereby rotate the base frame about the axis of the post of the opposite leg 120.

When the base frame is shifted sufficiently from its raised position toward its lowered position as to bring the base frame into contact with the sheet of photosensitive material supported by the work surface, it is desirable that no movement of the work carriage 38 be permitted. As part of a means for inhibiting movement of the work carriage when the base frame is in such lowered position, a limit switch 154, as shown in FIG. 21, is provided. This limit switch is mounted to the main frame 82 and has an operating arm 156 contacting an associated mounting pad 126 of the base frame 84. The limit switch 154 has a set of contacts which are open when the operating arm 156 is in the position illustrated in FIG. 21 and which are closed after the base frame 84 is moved a predetermined distance downwardly from the FIG. 21 position.

As mentioned previously, the base frame 84 serves to receive and hold the master photomask 50 and the light unit 86. The construction of the light unit 86 is best shown in FIGS. 11 and 22 and 23. The construction of the photomask is shown in FIGS. 12 and 13 and the manner in which the light source 86 and photomask are normally assembled with the base frame is best shown in FIG. 24. Considering first the photomask 50 of FIGS. 11 and 13, this photomask consists of a plate 158 of glass having a layer of opaque material 160 on its bottom surface. The opaque material 160 does not entirely cover the bottom surface and instead defines a pattern of opaque and transparent areas which create the master image as discussed above in connection with FIG. 4. The plate 158 is of a rectangular shape closely conforming to the rectangular shape of the opening 94 in the base frame so that when the master plate is placed in the base frame its edges are separated from the edges of the opening 94 by relatively small spaces. Fixed to each side of the plate 156, as by cement, is an L-shaped guide member 162 having an opening 164 which slidably receives the associated guide pin 98 of the base frame. The two guide members 162, 162 and the two cooperating guide pins 98, 98, therefore, accurately locate the plate 158 relative to the base frame while allowing the plate to move a slight distance vertically relative to the base frame.

Around the four edges of the plate 158 is a sealing and supporting gasket in the form of a strip 166 of flexible resilient material. Along each edge of the plate 158 the strip 166 partly overlies and is cemented to the plate. The remainder of the strip extends outwardly beyond the plate and, when the plate 158 is in position on the base frame, the outwardly extending portion of the strip 166 engages the adjacent shoulder 96 of the base frame to vertically support the plate from the base frame. Additionally, the seal strip 166 of the plate 158 provides a pneumatic seal between the plate and the base frame and also because of its resilient or flexible nature allows the plate 158 to move a small distance vertically relative to the base frame.

Referring to FIGS. 11, 22 and 23, the light unit 86 is of a rectangular shape and of a size similar to that of the master photomask 50. The unit is made up of a lower housing 168 and an upper housing 170 both made of sheet metal or other sheet material. The lower housing 168 is of an inverted cup shape and includes a flat rectangular upper wall 172 and, extending downwardly from the edges of the upper wall 172, two side walls 174, 174 and two end walls 176, 176. Contained within the bottom housing 168 is an electro-luminescent panel 178 which serves as the light source for illuminating the master photomask 50, the panel 178 comprising the light source 52 illustrated in FIG. 4. Below the electroluminescent panel 178 are a number of marginal strips 180, 180 located adjacent the side walls 174, 174 and end walls 176, 176. The strips 180, 180 are fixed to the housing 168 and serve to retain the electro-luminescent panel in place in the housing. When the light unit 86 is in place on the base frame of the contact printer, the strips 180, 180 rest on the seal strip 166 of the associated photomask and thereby support the electroluminescent panel 178 a slight distance above the top surface of the photomask. As shown best in FIG. 22, each side wall 174 of the bottom housing is notched midway along its length, as indicated at 182, to accom modate the associated guide member 162 of the underlying photomask 50.

The upper housing 170 of the light unit, as best illustrated in FIG. 22, is also of a generally inverted cup shape and is fixed to the lower housing 168 by a number of fasteners 184, 184. Within the top housing 170 is a circuit board 186 which provides the electrical control or logic circuitry associated with the light unit. As part of this control circuitry the light unit 86 includes a manually adjustable knob 188 by means of which the exposure time of the unit may be adjusted.

Having now described in some detail the construction of the contact printer 42 of FIG. 1, its operation may be considered. For this purpose reference is made to FIGS. 25, 26 and 27 which show the basic parts of the contact printer in somewhat schematic form and show the relative positions of these parts during different phases of one operating cycle of the printer. FIG. 25 shows the contact printer in its non-printing condition wherein the base frame is in its fully raised position relative to the main frame. With the base frame in this position, the contact printer may be moved by the work carriage 38 to any desired position relative to the sheet of photosensitive material 34. After the contact printer is brought into registry with a given area of the photosensitive surface which is to be exposed thereby, the work carriage 38 is held stationary and the solenoids 132, 132 are energized to move the base frame 84 downwardly relative to the main frame 82. As the base frame moves downwardly the sealing gasket 102 on the lower face of the base frame eventually contacts the surface of the underlying photosensitive material and creates a pneumatic seal between the photosensitive material and the base frame. The position of the base frame at this point in the operation of the device is shown in FIG. 26.

At the same time as the solenoids 132, 132 are energized the valve associated with the vacuum supply is operated to supply a vacuum to the vacuum tube 106 communicating with the bottom surface of the base plate. Therefore, after the gasket 102 contacts the photosensitive material the space between the photosensitive material and the master photomask is evacuated to create a pressure differential across the photomask and part of the base frame causing the photomask to be urged downwardly into direct contact with the surface of the photosensitive material and also drawing the base plate further downwardly toward the photosensitive material. This is the final or printing position of the photomask and is shown in FIG. 27. From this figure, it should be noted that the photomask in the printing position is displaced slightly downwardly relative to the base frame from its normal position. That is, as the space below the photomask is evacuated the seal gasket 166 resiliently flexes to allow the photomask to move downwardly relative to the base frame into direct firm engagement with the surface of the photosensitive material. Thus, when the photomask is in direct printing contact with the photosensitive material, it is held in such condition solely by the atmospheric pressure exerted thereon and no substantial forces are exerted be tween the photomask and the remaining structure of the contact printer or work carriage which would tend to distort the photomask and cause inaccuracies in the exposure. With the photomask in the printing to sition shown in FIG. 27 the electro-luminescent panel of the light unit is energized for a predetermined time to illuminate the photomask and expose its image on the photosensitive material. After this exposure is complete, the vacuum is released and the base plate allowed to return to its normal raised position to enable the contact printer to be moved to a new area of the photosensitive material. Thereupon the above-described exposure process may be repeated.

FIG. 28 shows schematically the basic parts of a logic circuit used to control the operation of the previously described contact printer 42. Referring to this figure, when the contact printer is to be operated to create an exposure, a start cycle signal is supplied on a line 190 to a flip-flop 192. This sets the flip-flop 190 and supplies an output signal to another flip-flop 194 and to an AND gate 196. The flipflop 194 is thereupon set and provides an output signal which energizes the two solenoids 132, 132 to move the base frame 84 downwardly toward the printing position. It also operates a solenoid operated valve 196 in a line from a vacuum source 198 to the vacuum tube 106 to cause the vacuum source to be connected to the tube 106. As the frame 84 reaches its lowered position the limit switch 154 is closed to supply an additional enabling signal to the AND gate 196 and also to provide an inhibit carriage movement signal which is supplied to the controller 46 of FIG. 1, or other control instrumentality, to condition such controller or other control instrumentality to prevent movement of both the main carriage 36 and work carriage 38. A short time after the base frame reaches its lowered position the vacuum source 198 will have evacuated the space between the photomask and the photosensitive surface to a given predetermined low pressure level at which the photomask will be firmly pressed against the photosensitive surface. At this predetermined low pressure level the vacuum switch 118 operates to set an associated flip-flop 200 to produce another enabling signal for the AND gate 196. At this time with all input terminals of the AND gate 196 enabled, an output is produced from the latter gate causing the triggering of an adjustable oneshot, multivibrator 202, the time duration of which is controlled by the control knob 188 of the light unit. A pulse of the desired time duration is accordingly sent to the light unit 86 to energize the electro-luminescent panel for such time duration. Thereafter, clear signals are sent to the various flip-flops to return the device to its initial condition.

The electroluminescent panel 178 of the light unit 86 is one having a single light emitting area coextensive with its entire face. That is, when the panel is energized, light is emitted from the entire downwardly facing surface thereof to illuminate the entire area of the underlying master photomask 50. If desired, however, in an alternate embodiment of the contact printer of this invention the electroluminescent panel of the light unit may be divided into a plurality of discrete separately energizable light emitting areas each overlying and registering with a respective one of acorresponding plurality of discrete areas of an associated photomask. Therefore, by energizing selected ones of the areas of the electroluminescent panel, corresponding selected ones of the discrete areas of the photomask may be illuminated. Such arrangement makes possible the use of the contact printer, in a photo composition mode, to compose an artwork by exposing different portions of the artwork during a number of operations of the contact printer.

FIG. 29 shows a light unit 204 having a segmented electroluminescent panel 206 adapting the contact printer previously described for use in photo composition work. The light unit 204 is essentially similar to the light unit 86 except for the replacement of the nonsegmented electroluminescent panel 178 of the unit 86 by the segmented panel 206. Parts of the unit 204 which are identical to parts of the unit 86 have been given the same reference numerals as in the preceding figures and need not be redescribed. The panel 206 is divided into 24 separate segments or discrete areas 208, 208 as indicated by the broken dividing lines 210, 210. Each segment 208 of the panel has its own pair of input leads, not shown, and by energizing the input leads of any one segment 208 such segment may be energized separately from the other segments. Of course, a number of segments may be simultaneously energized to simultaneously illuminate a corresponding number of discrete areas of the photomask.

FIG. 30 shows a representative master photomask divided into a number of discrete areas corresponding to the segments of the electroluminescent panel 206 and intended for use therewith. Referring to FIG. 30, the illustrated photomask is indicated at 212 and is divided into 24 separate discrete areas 214, 214 each of which underlies and registers with a respective one of the segments 208, 208 of the electroluminescent panel when the light unit 204 and photomask 212 are in operative position on the base frame of the contact printer. Each discrete area 214 of the photomask is intended to be illuminated either by itself or in combination with several other areas of the photomask. For example, the nine areas marked 214a, 214a are intended to be illuminated separately and each contains a small image located entirely within its area. On the other hand, the three areas marked 214b, 214k are intended to be energized simultaneously and together define an image spread over parts of all three of the areas 214b, 2l4b. Likewise, the four areas marked 2140, 214a are intended to be illuminated simultaneously and together define a single image spread thereover. Similarly, the two areas 214d, 214d are intended to be illuminated simultaneously, and the six areas 214e, 2142 are intended to be illuminated simultaneously.

The light unit of FIG. 29 and the photomask of the type shown in FIG. 30 may be used in the contact printer 42 of FIG. 1 in a photo composition mode to either create complete artworks entirely through the use of the contact printer or to complete only skeletonal artworks later completed through use of the second photoexposure device 44.

FIG. 31 shows a modification of the control circuit of FIG. 28 used to adapt the FIG. 28 circuit to use with a segmented electroluminescent panel and photomask such as shown by FIGS. 29 and 30. Referring to FIG. 31, the adjustable one-shot, multi-vibrator there illustrated is the same multi-vibrator 202 as shown in FIG. 28, and the circuit used to trigger the multi-vibrator 202 is the same as that of FIG. 28 and is not repeated in FIG. 31. However, instead of the output of the multivibrator 202 going directly to the electroluminescent panel, as in FIG. 28, the output, in the circuit of FIG. 31, is connectible to the various segments or discrete areas 208, 208 of the panel 206 through a plurality of solenoid operated switches 216, 216 and a patch board 218. The patch board 218 is or may be located in the upper housing of the light unit and includes an output terminal for energizing each lamp segment 208 and an input terminal from each switch 216. By means of jumpers, such as indicated at 220, 220, any switch 216 may be electrically connected to any one or more of the segments 208, 208 so as to energize such segments when the switch is closed, and such interconnections may be readily changed at will.

Each switch 216 is operated by an associated flip-flop 222 having an input line 224 from the controller 46. Each time the contact printer is operated the controller supplies signals to one or more of the input lines 224, 224 to set the associated flip-flop or flip-flops 222, 222 and to thereby close the associated switch or switches 216, 216. Subsequently, when the adjustable one-shot, multi-vibrator 202 is triggered the output pulse therefrom is transmitted to each segment 208 associated with a closed switch 216 through a jumper 220 in the patch board 218 to illuminate such segment. Accordingly, it will be appreciated that by proper programming of the patch board 218 and of the signals supplied to the input lines 224, 224 from the computer, during each operation of the contact printer any selected one or more of the sections 208, 208 may be energized to thereby illuminate corresponding areas of the associated photomask.

I claim:

1. A mechanism for exposing an artwork on a photosensitive surface, said mechanism comprising means providing a work surface for supporting a sheet of material with a photosensitive surface, a contact printing device, a line drawing device, and means including automatic controller for moving both said contact printing device and said line drawing device in a plane parallel to said work surface to being said contact printing device into registry with selected areas of said photo sensitive surface and to move said line drawing device along desired lines on said photosensitive surface, said contact printing device including means operable when said contact printing device is held stationary relative to said photosensitive surface for exposing a predetermined portion of an artwork on the area of said photosensitive surface registered therewith, said contact printing device further including a light source and a photomask arranged parallel to said work surface and located between said work surface and said light source, said photomask being generally planar and being divided into a number of discrete areas, and said light source including means for illuminating selected ones of said discrete areas of said photomask, and said line drawing device including means for directing a spot of light onto said photosensitive surface as said line drawing device is moved relative to said photosensitive surface to cause the exposure of a line on said photosensitive surface.

2. A mechanism for exposing an artwork on a photosensitive surface, said mechanism comprising means providing a work surface for supporting a sheet of material with a photosensitive surface, a contact printing device, a line drawing device, and means for moving both said contact printing device and said line drawing device in a plane parallel to said work surface to bring said contact printing device into registry with selected areas of said photosensitive surface and to move said line drawing device along desired lines on said photosensitive surface, said contact printing device including means operable when said contact printing device is held stationary relative to said photosensitive surface for exposing a predetermined portion of an artwork on the area of said photosensitive surface registered therewith, and said line drawing device including means for directing a spot of light onto said photosensitive surface as said lme drawing device is moved relative to said photosensitive surface to cause the exposure of a line on said photosensitive surface, said contact printing device including a photomask arranged parallel to said work surface and a light source in the form of an electro-luminescent panel, said photomask being located between said work surface and said electro luminescent panel so that when said electroluminescent panel is energized said photomask is illuminated thereby to expose an image of said photomask on the photosensitive surface of the sheet of material supported by said work surface, said photomask being generally planar and being divided into a number of discrete areas, said electro-luminescent panel being arranged in a plane parallel to said photomask and also being divided into a number of discrete areas each registering with a respective one of said discrete areas of said photomask, and means for selectively energizing said discrete areas of said electro-luminescent panel to selectively illuminate corresponding ones of said discrete areas of said photomask. 

1. A mechanism for exposing an artwork on a photosensitive surface, said mechanism comprising means providing a work surface for supporting a sheet of material with a photosensitive surface, a contact printing device, a line drawing device, and means including automatic controller for moving both said contact printing device and said line drawing device in a plane parallel to said work surface to being said contact printing device into registry with selected areas of said photosensitive surface and to move said line drawing device along desired lines on said photosensitive surface, said contact printing device including means operable when said contact printing device is held stationary relative to said photosensitive surface for exposing a predetermined portion of an artwork on the area of said photosensitive surface registered therewith, said contact printing device further including a light source and a photomask arranged parallel to said work surface and located between said work surface and said light source, said photomask being generally planar and being divided into a number of discrete areas, and said light source including means for illuminating selected ones of said discrete areas of said photomask, and said line drawing device including means for directing a spot of light onto said photosensitive surface as said line drawing device is moved relative to said photosensitive surface to cause the exposure of a line on said photosensitive surface.
 2. A mechanism for exposing an artwork on a photosensitive surface, said mechanism comprising means providing a work surface for supporting a sheet of material with a photosensitive surface, a contact printing device, a line drawing device, and means for moving both said contact printing device and said line drawing device in a plane parallel to said work surface to bring said contact printing device into registry with selected areas of said photosensitive surface and to move said line drawing device along desired lines on said photosensitive surface, said contact printing device including means operable when said contact printing device is held stationary relative to said photosensitive surface for exposing a predetermined portion of an artwork on the area of said pHotosensitive surface registered therewith, and said line drawing device including means for directing a spot of light onto said photosensitive surface as said line drawing device is moved relative to said photosensitive surface to cause the exposure of a line on said photosensitive surface, said contact printing device including a photomask arranged parallel to said work surface and a light source in the form of an electro-luminescent panel, said photomask being located between said work surface and said electro-luminescent panel so that when said electro-luminescent panel is energized said photomask is illuminated thereby to expose an image of said photomask on the photosensitive surface of the sheet of material supported by said work surface, said photomask being generally planar and being divided into a number of discrete areas, said electro-luminescent panel being arranged in a plane parallel to said photomask and also being divided into a number of discrete areas each registering with a respective one of said discrete areas of said photomask, and means for selectively energizing said discrete areas of said electro-luminescent panel to selectively illuminate corresponding ones of said discrete areas of said photomask. 